The North Atlantic Treaty Organization is considering a return to a Cold War-era naval command in response to increased Russian submarine activity in the Arctic, and to secure Atlantic sea lanes in case of a conflict, The Wall Street Journal reports.

A group of high-ranking officers from NATO countries, including U.S. Marine Gen. Joseph Dunford, the chairman of the Joint Chiefs, met in Brussels recently to get briefed on a command structure review. This included “options” for the Atlantic Command, the Journal reported.

If conflict were to arise between the U.S. or Europe and Russia, the Atlantic sea lanes could prove difficult to maintain against Russia’s submarines. According to “military planners and defense experts,” NATO surveillance of the Arctic and North Atlantic is unable to detect Russia’s modern submarine fleet.

The Center for a New American Security, an American think tank, briefed NATO Secretary General Jens Stoltenberg of a wargame simulation during which Russian subs break up an alliance military drill, attack a transport ship for the U.S. military, and sever an undersea cable in the Atlantic and interrupting worldwide communications, the Journal reported.

NATO military committee chairman Czech Army Gen. Petr Pavel told the Journal that “We have to assess potential threats from any direction, including the North Atlantic, including the Arctic,” in light of Russia’s tactics and unrelated terrorist threats.

President Donald Trump is set to deliver a speech next Thursday in which he’s expected to address his feelings on the partnership. During the campaign he called NATO “obsolete,” but said more recently that taking office has changed his view. He has yet to offer his full support for the treaty’s Article 5, which states that any attack on a member nation is considered an attack on all member nations.

“The problem in the plan is that President Trump is the only president who has not yet explicitly endorsed Article 5,” the Brookings Institution’s Thomas Wright told CNBC. “I understand that is not an accident.”

Julie Smith, national security aide to former Vice President Joe Biden, added that Trump “has never said, like Pence, like Mattis, that U.S. commitment to Article 5 is rock solid, and allies want to hear that at this summit.”